Clinical and Laboratory Characteristics of Patients With Erythema Nodosum.

Erythema nodosum (EN) represents an acute, erythematous nodular eruption that is generally found on the lower aspects of the legs. Despite the variety of triggering factors, the clinical findings of EN are classic. It is often hard to determine which patients have an underlying systemic disorder. The aim of this study was to investigate clinical and laboratory parameters in patients with EN, especially those with an underlying systemic disorder. A total of 43 patients diagnosed with EN at an adult and children's hospital were retrospectively reviewed for triggering factors, any underlying systemic diseases, clinical features, laboratory parameters, treatment modalities, and disease outcome. The mean age of the patients was 40.91±15.57 years (minimum 7 years, maximum 71 years). Patients with an underlying systemic disorder were grouped as complicated EN (CEN), patients without an underlying disorder were grouped as non-complicated EN (NCEN). Patients with EN more frequently presented with more nonpretibial localizations than patients with NCEN (P=.023). Platelet levels in patients with CEN were significantly higher than in patients with NCEN (P=.036). Erythrocyte sedimentation rate, C-reactive protein, and procalcitonin levels did not differ among the two groups (P>.05). Hospitalization shortened the active disease duration (P=.046). EN lesions present on the nonpretibial area, which may be a clue for systemic associations of the disease. The presence of elevated platelet levels may indicate systemic inflammatory and infectious diseases in patients with EN. Procalcitonin, which is a marker for systemic infection, was not helpful in detecting chronic infections such as tuberculosis or systemic fungal infections in patients.